Waterbeds are well known as devices comprising a fluid filled envelope upon which a person may recline with the person comfortably supported thereon as a result of fluid displacement.
Many attempts have been made to reduce the effects of wave motion generated in waterbed mattresses. For example wave reducing devices have been proposed by U.S. Pat. No. 4,204,289 to Fogel, U.S. Pat. No. 4,325,152 to Carpenter and U.S. Pat. No. 4,475,257 to Phillips. These devices have suffered a number of disadvantages.
In Fogel and Carpenter, baffles are coupled to the bottom sheet of the envelope forming the waterbed mattress, making the envelope difficult to manufacture. With the baffles coupled to the bottom sheet, forces arising in dampening wave motion are transmitted to the seams joining the baffles to the bottom sheet, increasing the incidence of tearing of the bottom sheet and leakage of the envelope.
U.S. Pat. No. 4,475,257 to Phillips teaches a "hydraulic" mattress. Compartments within the mattress become completely closed with the closed compartments, due to hydraulic pressure therein, preventing further compression of the mattress. However, the compartments are formed from vinyl sheeting which cannot withstand the considerable hydraulic forces generated when a person's weight is concentrated on a few such compartments. After repeated use, the walls of the compartment typically rupture. Moreover, when the compartments of Phillips become completely closed, the compartments feel relatively hard to a user.
Accordingly, it is an object of the present invention to at least partially overcome the disadvantages of known wave reducing devices by providing a free floating damping structure comprising a bottom panel of flexible sheet material with a plurality of tubular structures extending upwardly therefrom wherein fluid flow restricting ports are provided through the top, bottom and side walls of the tubular members.
Another object is to provide an improved damping structure with effectively dampens wave motion within a waterbed mattress.
In one of its aspects, the present invention provides, in a waterbed mattress comprising a top sheet and a bottom sheet joined together to form a sealed envelope filled with liquid, an improvement comprising a damping structure floating freely within the envelope to dampen wave action in the mattress, the damping structure comprising a bottom panel of flexible sheet material extending over substantially the entirety of the upper surface of the bottom sheet, a plurality of vertically disposed tubular structures coupled to the bottom panel to each extend independently upwardly therefrom, the tubular structures distributed over the bottom panel, each tubular structure having side walls of flexible material and a top panel with the side walls coupled to the bottom panel to close a bottom end of the tubular structure and with the side walls coupled to the top panel to close a top end of the tubular structure, the top panel, bottom end and side walls of each tubular structure having, respectively, top port means, bottom port means, and side port means therethrough to permit liquid flow into and out of the tubular structure, each top panel comprising a thin plate of low density floatation means to float the top end of the tubular structure upwardly into engagement with the undersurface of the top sheet and restrict liquid flow through the top port means, the tubular structures being of a length that:
(a) when the mattress is uncompressed, the bottom panel hangs downwardly from the top panels with the bottom panel spaced from the uppersurface of the bottom sheet, and
(b) when the mattress is compressed, the bottom panel engages the upper surface of the bottom sheet restricting liquid flow through the bottom port means.
The present invention provides a damping structure to float freely within the envelope of a waterbed mattress to dampen wave action therein. The damping structure comprises a bottom panel of flexible sheet material with a number of vertically disposed tubular structures or elements extending upwardly therefrom. Each tubular structure is coupled to the bottom panel with a portion of the bottom panel closing the bottom end of the tubular structure. The tubular structure has a side wall and is closed at a top end by a top panel. The top panels are buoyant and serve to float the tubular structure upward suspending the bottom panel from the tubular structures spaced from the bottom sheet of the waterbed envelope. Ports are provided through the top end, side walls and bottom end of the tubular structures to permit fluid flow into and out of the tubular structures. While the ports through the side walls are, even when the mattress is compressed in use, open to permit flow into and out of the tubular structures, the ports in the top end are normally substantially closed by engagement of the top ports with the upper sheet of the envelope and the ports in the bottom end become effectively closed when the mattress is compressed in use so as to bring portions of the bottom panel comprising bottom ends of tubular elements into engagement with the bottom sheet of the envelope.
The bottom panel effectively divides the mattress into a lower compartment therebelow and on upper compartment containing the tubular structures thereabove. Preferably, the bottom panel extends substantially co-extensively over the area of the envelope. Preferably, the tubular structures cumulatively retain a major portion of the total liquid in the envelope, preferably at least 70%. Preferably the upper compartment should be of substantially greater volume than the lower compartment, with for example the upper compartment comprising at least 80% of total volume of the envelope.